Tabs moving out of order randomly

I'm unclear exactly how to reproduce this. My setup is a single window with several tabs. Sometimes, a tab will move out of order in the list. When I Command-Shift-] or Command-Shift-[ to where the tab should be, it goes to the tab, but its position in the tab bar is in the wrong spot. The tabs also seem to keep their original Command-number shortcuts. I can drag the tab back to where it is supposed to be.